Free written scope consultation - allowances, timeline, and change-order rules on paper before a single trade is scheduled
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Before
AfterFast, Reliable Home Additions & ADU Across Los Gatos
A typical home addition in Los Gatos runs $45,000-$130,000, while ADU construction ranges from $90,000-$220,000 depending on slope, fire code requirements, and whether the lot triggers Hillside Development Standards. Most Los Gatos projects take 4-8 months from permit to final inspection, with hillside lots adding 2-4 months for geotechnical review. Call (831) 704-1211 to schedule your free estimate - we quote a flat written price before any work starts, every time.
We serve Los Gatos from our San Francisco Bay Area dispatch office, with crews running daily to hillside lots off Kennedy Road and Highway 9, downtown Victorians near North Santa Cruz Avenue, and the flatland ranches along Los Gatos-Almaden Road. The west-facing fog off the Santa Cruz Mountains, the WUI fire code on slopes above 500 feet, and the Historic Preservation Committee’s design review downtown - these three conditions shape every addition we spec in this town. Our Home Additions & ADU team has rebuilt rotted fascia, reframed single-wall bungalows, and navigated dual permit tracks enough times to know where the delays hide.
Why Rowan Construction Group Campbell Is Los Gatos’s Preferred Home Additions & ADU Company
We’ve delivered 4,000-plus projects since 2007, every one with a written price before work started and a documented photo record when the crew left. Los Gatos homeowners find us the same way they research appliances - they read the three-star reviews, then call to see if we’ll put a number in writing. We do. Under Clause 1 of The Haven Standard, the price is written before anyone picks up a tool.
Our crews are background-checked and uniformed; a live person answers calls 24/7. Dispatch and scheduling are coordinated from our San Francisco Bay Area office, with Los Gatos crews carrying stainless fasteners and marine-grade hardware as standard - not an upgrade - because west-facing fog on hillside lots destroys inland-spec materials within a few seasons. The 365-Day Done Right Promise is printed on every contract: if it is not done right, we make it right.
We also offer a Free Second Opinion on any written estimate. Bring a competitor’s quote and we’ll review it line by line at no charge. No change proceeds without a signed change order - the administrative discipline Haven acquired Rowan for, and the reason our projects finish within a few percent of the agreed price.
Our Home Additions & ADU Services in Los Gatos
ADU Design & Permitting
Los Gatos ADU permits require navigating either the Town’s Hillside Development Standards or Historic Preservation Committee review - sometimes both on split-zoned properties. We scope geotechnical reports, visual impact studies, and WUI fire-code compliance from the first drawing set, because adding them after submittal kills timelines. A detached ADU on a hillside lot above 500 feet needs a separate Hillside Development Permit on top of the building permit; we build that 2-4 month buffer into every schedule we write. Our design package includes ignition-resistant venting specs, non-combustible siding selections from James Hardie, and defensible-space grading plans that satisfy CAL FIRE and the Town inspector both.
Garage Conversion ADU
Garage conversions in Los Gatos run $30,000-$80,000, with the low end covering flatland ranches and the high end addressing hillside garages with cripple-wall foundations and unreinforced chimneys. We rebuilt a garage-conversion ADU on a steep lot off Kennedy Road in Los Gatos, where the original single-wall framing, unreinforced chimney, and a fascia that had rotted through from west-facing fog dictated a full rough-in redo before insulation. We ran stainless fasteners and marine-grade hardware, set ember-resistant vents per WUI code, and documented every change order in writing before the geotech re-check cleared the slope. The client’s punch list closed clean after inspection sign-off, and the new space has held through two wet winters without a hint of the rot we tore out.
New Detached ADU
Detached ADUs on Los Gatos hillside lots face the full regulatory stack: geotechnical report, visual impact study, Hillside Development Permit, plus WUI ignition-resistant construction standards. We spec Type A roofing, ember-resistant venting, and non-combustible siding from the foundation up - the same spec that passes CAL FIRE inspection and holds up to marine fog. The price gap between coastal-spec and inland-spec hardware is real: stainless fasteners and marine-grade finishes add 8-15% upfront, but inland-grade hardware on a west-facing hillside fails within 3-5 years, and the rework costs more than the original upgrade. We put both specs in writing so you can see the ten-year math.
Junior ADU & Interior Conversion
Junior ADUs - conversions within the existing footprint, no new foundation - avoid Hillside Development Standards but still trigger historic review downtown and may require seismic reinforcement in pre-1940s homes. We open floors and walls with the structural engineer on-site, because cripple-wall foundations and single-wall framing in downtown Victorians won’t carry new load-bearing walls without retrofit. The documented photo record shows you what we found, what we reinforced, and what the inspector signed off on.
Room Additions
Room additions on Los Gatos flatland ranches are straightforward structurally; the same job on a hillside lot above 500 feet needs the full geotechnical and visual-impact package. We price both paths in writing so there’s no surprise when the survey comes back. Our room addition quotes include rough-in for electrical and plumbing, insulation to Title 24 standards, and finish selections from our fifty-plus vetted brands - KraftMaid and Wellborn cabinets if you’re building out a master suite, Cambria countertops if the addition includes a wet bar.
What happens when you call
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A real person answersNo phone trees - you reach a local pro.
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You get an upfront price rangeHonest numbers before anyone is dispatched.
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A background-checked tech heads outLicensed & insured, dispatched right away.
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You approve before work beginsNothing starts until you say go.
Before
AfterTrusted Brands We Service in Los Gatos
We source across fifty-plus vetted brands, which lets us quote honest numbers rather than inflated ones. For Los Gatos additions and ADUs, we regularly specify James Hardie fiber-cement siding for WUI compliance on hillside lots, KraftMaid and Wellborn cabinetry for interior conversions, and Cambria quartz surfaces for kitchenette and wet-bar builds. We stock hardware and finishes locally for Los Gatos projects, so material lead times don’t extend schedules that are already padded for geotechnical review. Every brand selection is documented in the written scope with model numbers and warranties - no “or equal” substitutions without a signed change order.
Common Home Additions & ADU Problems We See in Los Gatos Homes
- Marine fog rot on west-facing hillside structures. West- and north-facing additions above 500 feet catch sustained fog off the Santa Cruz Mountains, accelerating wood rot and mold intrusion. Contractors who spec inland-grade hardware and standard vents end up repairing both problems within a few seasons. We run stainless fasteners and marine-grade finishes from day one.
- Dual regulatory delays on split-zoned properties. WUI fire code on the slopes and Historic Preservation Committee design review downtown means exterior additions that pass one set of requirements can be flagged in the other. We scope both tracks from the first drawing set to avoid the 2-4 month catch-up.
- Hidden seismic issues in pre-1940s downtown homes. Cripple-wall foundations and unreinforced chimneys won’t carry new load-bearing additions without retrofit. We open subfloors with the structural engineer present, document what we find, and write the change order before proceeding.
- Steep-slope drainage failures on Kennedy Road and Highway 9 lots. Hillside additions without proper grading and permeable surface design send water into foundations during winter storms. Our site prep includes drainage plans that satisfy the Hillside Development Standards inspector and prevent the callbacks we’ve seen on jobs that skipped this step.
Pricing for Home Additions & ADU in Los Gatos, CA
These are the ranges we quote in writing before any work starts. Every price is flat, with a written scope and written warranty. No “call for a quote” - Clause 1 of The Haven Standard requires the number upfront.
| Service | Price Range (Los Gatos) |
|---|---|
| Home Addition (coastal/WUI-spec) | $45,000-$130,000 |
| ADU Construction (coastal/WUI-spec) | $90,000-$220,000 |
| Garage Conversion ADU | $30,000-$80,000 |
What moves the price: slope and geotechnical complexity (hillside lots add 15-30% for the extra permits and structural work), fire-code compliance level (WUI zones require Type A roofing, ember-resistant venting, and non-combustible siding), and finish selections (Cambria vs. standard quartz, KraftMaid vs. stock cabinetry). The cheap spec costs more within a decade on a west-facing hillside - we’ve torn out enough rotted fascia and corroded fasteners to know. Call (831) 704-1211 for an exact quote on your specific lot; estimates are free and include a line-item breakdown.
We Also Serve Cities Near Los Gatos
Our crews run daily to Los Gatos, Saratoga, Campbell, Cupertino, and Santa Clara. Each city has its own permit timeline and code emphasis - Saratoga shares Los Gatos’s hillside challenges but not its historic overlay, while Campbell and Santa Clara are flatland jurisdictions with faster turnaround. We adjust the spec and the schedule to match.
Serving Los Gatos, CA - Our Local Coverage Area
We’re based in the Los Gatos area and know this community well. Use the map below to see our service coverage - if you’re nearby, we can almost certainly help.
FAQs - Home Additions & ADU in Los Gatos
Yes. Any addition or new structure on a lot above roughly 500 feet elevation triggers the Town’s Hillside Development Standards, requiring a geotechnical report, a visual impact study, and a separate Hillside Development Permit in addition to the standard building permit. We scope all three from the first drawing set and build the 2-4 month timeline into every schedule we write. Call (831) 704-1211 to review your lot’s elevation and permit path.
The same square footage runs 15-30% higher on Los Gatos hillside lots due to three factors: the Hillside Development Permit process (geotechnical report, visual impact study, extended review), WUI fire-code compliance (Type A roofing, ember-resistant venting, non-combustible siding), and the structural reality of building on steep slopes with drainage and access challenges. Campbell and San Jose flatland projects skip all three. We quote both spec levels in writing so you can see where the money goes. Call (831) 704-1211 for a line-item breakdown.
Yes, with the right spec and sequencing. We address rot-prone existing structures with full rough-in redo, replace single-wall framing with seismic-compliant construction, and run stainless fasteners and marine-grade hardware on every west- and north-facing exposure. The geotechnical report governs foundation design, and we don’t pour until it clears. Call (831) 704-1211 to walk your specific slope and framing condition.
Marine-grade aluminum or fiberglass window frames, never standard vinyl or uncoated steel - the fog off the Santa Cruz Mountains corrodes inland-spec frames within 3-5 years. Railings need hot-dip galvanized or stainless hardware with sealed joints; weep holes and drainage channels must be designed in, not added after. We specify these in the written scope with brand and model numbers. Call (831) 704-1211 to review the exterior package for your exposure.
We scope both tracks from the first drawing set and run them in parallel rather than sequence. The Historic Preservation Committee reviews exterior aesthetics and materials; CAL FIRE and the Town building division review ignition resistance and structural compliance. Where requirements conflict - say, a historic-appropriate wood siding vs. WUI-mandated non-combustible cladding - we specify compliant alternatives (James Hardie fiber-cement with historic profiles) and document the resolution in writing before submittal. This dual-track approach avoids the 2-4 month delay of sequential review. Call (831) 704-1211 to discuss your property’s zoning layers.
Ready to price your project? Call (831) 704-1211 to schedule your free estimate. We’ll deliver a flat written price with a line-item scope, a written warranty, and a documented photo record as standard - because under The Haven Standard, the number comes first and the proof comes with it.
Written by Grant Rowan, Owner at Rowan Construction Group, serving Los Gatos since 2007.